A resistive voltage divider is a conventional circuit for dividing an input voltage. But achieving low power consumption in a resistive voltage divider is problematic in that the resistors within the resistive voltage divider must be fairly robust (e.g., 2 MΩ) to reduce the current conducted to ground. The resulting oversizing of the resistors makes them less prone to semiconductor process variations as compared to active devices such as transistors. Moreover, resistors are commonly formed using considerably lower doping levels as compared to active devices such that a resistive voltage divider is typically robust to temperature variations. But the oversizing of the resistors lowers density in the resulting integrated circuit due to the die area needed to provide such robust resistances.
In contrast to the die area demands from resistive voltage dividers, a switched-capacitor voltage divider provides a more compact alternative. The capacitors in a switched-capacitor voltage divider are open circuits with respect to conducting DC current such that the capacitors need not be oversized to lower power consumption. A switched-capacitor voltage divider is thus advantageously dense as compared to a resistive voltage divider. However, the transistor switches in a switched-capacitor voltage divider consume substantial dynamic power.
Accordingly, there is a need in the art for an improved switched-capacitor voltage divider that retains its density advantages yet is low-power (e.g., less than 0.5 μA).